Vehicle restraints are employed to prevent accidental movement of a truck away from a loading dock during a loading operation. When a truck is parked in front of a loading dock the rear end of the truck completely encloses the doorway in the loading dock with the result that the truck driver cannot observe the loading or unloading of cargo from the truck by a lift truck or other mechanical handling equipment. To prevent the truck from accidentally pulling away from the dock before the loading or unloading operation is completed, vehicle restraints have been used which are mounted on the loading dock and engage the ICC bar mounted at the rear end of the truck. The ICC bar is a bar beam that extends horizontally across the rear of the truck beneath the truck bed and is intended to prevent an automobile from underriding the truck in the event of a rear end collision.
Certain types of vehicle restraints, such as that disclosed in U.S. Pat. No. 4,488,325, employ a linear moving hook which is moved vertically along the front face of the dock from a lower storage position to an upper operative position where it engages the ICC bar. Other types of vehicle restraints employ a pivotable hook and are swung upwardly into engagement with the ICC bar.
Vehicle restraints are commonly used in conjunction with a dockboard. The conventional dock board is mounted in a pit or depression in the upper surface of the dock and includes a ramp which is hinged at its rear edge to the dock, while a lip is hinged to the front end of the ramp and is movable between a downwardly hanging pendant position and an extended position where it forms an extension to the ramp and serves to bridge the gap between the loading dock and the truck bed. When used with a dockboard, the vehicle restraint is mounted on the front face of the dock beneath the pit in which the dockboard is housed. With a vehicle restraint that utilizes a linear moving hook, an elongated guide mechanism is mounted on the dock face beneath the pit and the hook moves vertically in the guide mechanism from the lower storage position to the upper operative position.
The vertical height of an ICC bar above the ground may vary considerably depending upon the make and the type of truck involved. In order to affectively accommodate ICC bars of different heights, the guide mechanism, on which the hook is mounted for vertical movement, must have a substantial height, yet the guide mechanism should not extend above the bottom of the pit or it will interfere with the swinging action of the lip of the dockboard. Because of this, in certain installations that have a deep dockboard pit, the front face of the dock beneath the pit does not have sufficient vertical height to mount a conventional vehicle restraint.